The effect of a metal-back without a stem upon the fixation of a tibial prosthesis

Three methods of tibial component fixation without cement (as part of TKA) have been used at the London Hospital. All three methods have used the same polyethylene component fixed with two HDP (Day) pegs. A metal-back without a stem was added to the HDP in group 1. Group 2 consisted of an HDP-only component. In group 3 a stem was added to the metal-back used in group 1. Radiological comparison showed the fixation of the polyethylene component with metal back but no stem to be inadequate; the component tilted into varus more frequently than the other configurations. It is suggested that failure was due to the increased rigidity of the metal-backed component (as compared with the HDP only) and that the rigidity (and the resultant tendency to rock) can be offset by a stem. It is concluded that rigid (ie, metallic) tibial components should have a stem.